Method and apparatus or sensing environmental conditions

ABSTRACT

A wireless sensor includes a radio frequency (RF) receiving circuit operable to receive an RF signal having a carrier frequency of a plurality of carrier frequencies. The RF receiving circuit further includes a variable impedance where impedance of the variable impedance is a factor in establishing a resonant frequency of the RF receiving circuit. The wireless sensor further includes a processing module that is operable to determine a first value for a first impedance of the variable impedance for a known temperature based on the resonant frequency and the carrier frequency, determine a second value a second impedance of the variable impedance for an unknown temperature based on the resonant frequency and the carrier frequency, and determine a difference between the first and second values that corresponds to a change between the known temperature and the unknown temperature.

CROSS REFERENCE TO RELATED APPLICATIONS

The present U.S. Utility Patent Application claims priority pursuant to35 U.S.C. § 120 as a continuation of U.S. Utility application Ser. No.15/665,251, entitled “METHOD AND APPARATUS FOR SENSING ENVIRONMENTALCONDITIONS”, filed Jul. 31, 2017, issuing as U.S. Pat. No. 10,164,611 onDec. 25, 2018, which claims priority pursuant to 35 U.S.C. § 120 as acontinuation-in-part of U.S. Utility application Ser. No. 14/727,523,entitled “Method and Apparatus for Sensing Environmental ParametersUsing Wireless Sensor(s),” filed Jun. 1, 2015, now U.S. Pat. No.9,991,596, issued on Jun. 5, 2018, which claims priority pursuant to 35U.S.C. § 119(e) to U.S. Provisional Application No. 62/004,941, entitled“Pressure/Proximity Sensors Reference Design,” filed May 30, 2014; U.S.Provisional Application No. 62/004,943, entitled “Method and Apparatusfor Varying an Impedance,” filed May 30, 2014; U.S. ProvisionalApplication No. 62/011,116, entitled “Method and Apparatus for SensingWater Level Using Wireless Sensor(s),” filed Jun. 12, 2014; and U.S.Provisional Application No. 62/131,414, entitled “Method and Apparatusfor Variable Capacitor Control,” filed Mar. 11, 2015, all of which arehereby incorporated herein by reference in their entirety and made partof the present U.S. Utility Patent Application for all purposes.

U.S. Utility Patent application Ser. No. 14/727,523 also claims prioritypursuant to 35 U.S.C § 120 as a continuation-in-part of U.S. Utilityapplication Ser. No. 14/256,877, entitled “METHOD AND APPARATUS FORSENSING ENVIRONMENT USING A WIRELESS PASSIVE SENSOR”, filed Apr. 18,2014, now U.S. Pat. No. 9,785,807, issued on Oct. 10, 2017, which claimspriority pursuant to 35 U.S.C. § 119(e) to U.S. Provisional ApplicationNo. 61/814,241, entitled “RFID ENVIRONMENTAL SENSOR”, filed Apr. 20,2013; U.S. Provisional Application No. 61/833,150, entitled “RESONANTANTENNA”, filed Jun. 10, 2013; U.S. Provisional Application No.61/833,167, entitled “RFID TAG”, filed Jun. 10, 2013; U.S. ProvisionalApplication No. 61/833,265, entitled “RFID TAG”, filed Jun. 10, 2013;U.S. Provisional Application No. 61/871,167, entitled “RESONANTANTENNA”, filed Aug. 28, 2013; U.S. Provisional Application No.61/875,599, entitled “CMF ACCURATE SENSOR”, filed Aug. 9, 2013; U.S.Provisional Application No. 61/896,102, entitled “RESONANT ANTENNA”,filed Oct. 27, 2013; U.S. Provisional Application No. 61/929,017,entitled “RFID ENVIRONMENTAL SENSOR”, filed Jan. 18, 2014; U.S.Provisional Application No. 61/934,935, entitled “RFID ENVIRONMENTALSENSOR”, filed Feb. 3, 2014; all of which are hereby incorporated hereinby reference in their entirety and made part of the present U.S. UtilityPatent Application for all purposes.

U.S. Utility application Ser. No. 14/256,877 also claims prioritypursuant to 35 U.S.C. § 120 as a continuation-in-part of U.S. Utilityapplication Ser. No. 13/209,420, entitled “METHOD AND APPARATUS FORDETECTING RF FIELD STRENGTH”, filed Aug. 14, 2011, now U.S. Pat. No.8,749,319, issued on Jun. 10, 2014, which claims priority pursuant to 35U. S.C. § 119(e) to U.S. Provisional Application No. 61/428,170,entitled “METHOD AND APPARATUS FOR VARYING AN IMPEDANCE”, filed Dec. 29,2010 and U.S. Provisional Application No. 61/485,732, entitled “METHODAND APPARATUS FOR SENSING ENVIRONMENTAL CONDITIONS USING AN RFID TAG”,filed May 13, 2011, all of which are hereby incorporated herein byreference in their entirety and made part of the present U.S. UtilityPatent Application for all purposes.

U.S. Utility application Ser. No. 13/209,420 also claims prioritypursuant to 35 U.S.C. § 120 as a continuation-in-part of U.S. Utilityapplication Ser. No. 12/462,331, entitled “METHOD AND APPARATUS FORVARYING AN IMPEDANCE”, filed Aug. 1, 2009, now U.S. Pat. No. 8,081,043,issued on Dec. 20, 2011, which is a divisional of U.S. Utilityapplication Ser. No. 11/601,085, entitled “METHOD AND APPARATUS FORVARYING AN IMPEDANCE”, filed Nov. 18, 2006, now U.S. Pat. No. 7,586,385,issued on Sep. 8, 2009, all of which are hereby incorporated herein byreference in their entirety and made part of the present U.S. UtilityPatent Application for all purposes.

U.S. Utility application Ser. No. 14/256,877 also claims prioritypursuant to 35 U.S.C. § 120 as a continuation-in-part of U.S. Utilityapplication Ser. No. 13/209,425, entitled “METHOD AND APPARATUS FORDETECTING RF FIELD STRENGTH”, filed Aug. 14, 2011, now U.S. Pat. No.9,048,819, issued on Jun. 2, 2015, which claims priority pursuant to 35U.S.C. § 119(e) to U.S. Provisional Application No. 61/428,170, entitled“METHOD AND APPARATUS FOR VARYING AN IMPEDANCE”, filed Dec. 29, 2010 andU.S. Provisional Application No. 61/485,732, entitled “METHOD ANDAPPARATUS FOR SENSING ENVIRONMENTAL CONDITIONS USING AN RFID TAG”, filedMay 13, 2011, all of which are hereby incorporated herein by referencein their entirety and made part of the present U.S. Utility PatentApplication for all purposes.

U.S. Utility application Ser. No. 13/209,425 also claims prioritypursuant to 35 U.S.C. § 120 as a continuation-in-part of U.S. Utilityapplication Ser. No. 12/462,331, entitled “METHOD AND APPARATUS FORVARYING AN IMPEDANCE”, filed Aug. 1, 2009, now U.S. Pat. No. 8,081,043,issued on Dec. 20, 2011, which is a divisional of U.S. Utilityapplication Ser. No. 11/601,085, entitled “METHOD AND APPARATUS FORVARYING AN IMPEDANCE”, filed Nov. 18, 2006, now U.S. Pat. No. 7,586,385,issued on Sep. 8, 2009, all of which are hereby incorporated herein byreference in their entirety and made part of the present U.S. UtilityPatent Application for all purposes.

U.S. Utility application Ser. No. 14/256,877 also claims prioritypursuant to 35 U.S.C. § 120 as a continuation-in-part of U.S. Utilityapplication Ser. No. 13/467,925, entitled “ROLL-TO-ROLL PRODUCTION OFRFID TAGS”, filed May 9, 2012, which is a continuation-in-part of U.S.Utility application Ser. No. 13/209,425, entitled “METHOD AND APPARATUSFOR DETECTING RF FIELD STRENGTH”, filed Aug. 14, 2011, now U.S. Pat. No.9,048,819, issued on Jun. 2, 2015, which claims priority pursuant to 35U.S.C. § 119(e) to U.S. Provisional Application No. 61/428,170, entitled“METHOD AND APPARATUS FOR VARYING AN IMPEDANCE”, filed Dec. 29, 2010 andU.S. Provisional Application No. 61/485,732, entitled “METHOD ANDAPPARATUS FOR SENSING ENVIRONMENTAL CONDITIONS USING AN RFID TAG”, filedMay 13, 2011, all of which are hereby incorporated herein by referencein their entirety and made part of the present U.S. Utility PatentApplication for all purposes.

U.S. Utility application Ser. No. 13/209,425 also claims prioritypursuant to 35 U.S.C. § 120 as a continuation-in-part of U.S. Utilityapplication Ser. No. 12/462,331, entitled “METHOD AND APPARATUS FORVARYING AN IMPEDANCE”, filed Aug. 1, 2009, now U.S. Pat. No. 8,081,043,issued on Dec. 20, 2011, which is a divisional of U.S. Utilityapplication Ser. No. 11/601,085, entitled “METHOD AND APPARATUS FORVARYING AN IMPEDANCE”, filed Nov. 18, 2006, now U.S. Pat. No. 7,586,385,issued on Sep. 8, 2009, all of which are hereby incorporated herein byreference in their entirety and made part of the present U.S. UtilityPatent Application for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable

BACKGROUND OF THE INVENTION Technical Field of the Invention

This application relates generally to wireless data communicationsystems and more particularly to processing data representative ofenvironmental sensed conditions.

Description of Related Art

Wireless communication systems are known to include wirelesstransceivers that communication directly and/or over a wirelesscommunication infrastructure. In direct wireless communications, a firstwireless transceiver includes baseband processing circuitry and atransmitter to convert data into a wireless signal (e.g., radiofrequency (RF), infrared (IR), ultrasound, near field communication(NFC), etc.). Via the transmitter, the first wireless transceivertransmits the wireless signal. When a second wireless transceiver is inrange (e.g., is close enough to the first wireless transceiver toreceive the wireless signal at a sufficient power level), it receivesthe wireless signal via a receiver and converts the signal intomeaningful information (e.g., voice, data, video, audio, text, etc.) viabaseband processing circuitry. The second wireless transceiver maywirelessly communicate back to the first wireless transceiver in asimilar manner.

Examples of direct wireless communication (or point-to-pointcommunication) include walkie-talkies, Bluetooth, ZigBee, RadioFrequency Identification (RFID), etc. As a more specific example, whenthe direct wireless communication is in accordance with RFID, the firstwireless transceiver may be an RFID reader and the second wirelesstransceiver may be an RFID tag.

For wireless communication via a wireless communication infrastructure,a first wireless communication device transmits a wireless signal to abase station or access point, which conveys the signal to a wide areanetwork (WAN) and/or to a local area network (LAN). The signal traversesthe WAN and/or LAN to a second base station or access point that isconnected to a second wireless communication device. The second basestation or access point sends the signal to the second wirelesscommunication device. Examples of wireless communication via aninfrastructure include cellular telephone, IEEE 802.11, public safetysystems, etc.

In many situations, direct wireless communication is used to gatherinformation that is then communicated to a computer. For example, anRFID reader gathers information from RFID tags via direct wirelesscommunication. At some later point in time (or substantiallyconcurrently), the RFID reader downloads the gathered information to acomputer via a direct wireless communication or via a wirelesscommunication infrastructure.

In many RFID systems, the RFID tag is a passive component. As such, theRFID tag has to generate one or more supply voltages from the RF signalstransmitted by the RFID reader. Accordingly, a passive RFID tag includesa power supply circuit that converts the RF signal (e.g., a continuouswave AC signal) into a DC power supply voltage. The power supply circuitincludes one or more diodes and one or more capacitors. The diode(s)function to rectify the AC signal and the capacitor(s) filter therectified signal to produce the DC power supply voltage, which powersthe circuitry of the RFID tag.

Once powered, the RFID tag receives a command from the RFID reader toperform a specific function. For example, if the RFID tag is attached toa particular item, the RFID tag stores a serial number, or some otheridentifier, for the item. In response to the command, the RFID tagretrieves the stored serial number and, using back-scattering, the RFIDtag transmits the retrieved serial number to the RFID reader.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a communicationsystem in accordance with the present invention;

FIG. 2 is a schematic block diagram of an embodiment of a computingdevice in accordance with the present invention;

FIG. 3 is a schematic block diagram of an example of a sensor computingdevice communicating with a passive wireless sensor in accordance withthe present invention;

FIG. 4 is a schematic block diagram of another example of a sensorcomputing device communicating with a passive wireless sensor inaccordance with the present invention;

FIG. 5 is a schematic block diagram of an example of a plurality ofcomponents of a radio frequency (RF) receiving circuit in accordancewith the present invention;

FIG. 6 is a schematic block diagram of another example of a plurality ofcomponents of a radio frequency (RF) receiving circuit in accordancewith the present invention; and

FIG. 7 is a logic diagram of an example of determining a change in anenvironmental condition in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of a communicationsystem 10 that includes a plurality of sensor computing devices 12, aplurality of user computing devices 14, a plurality of passive wirelesssensors 16-1 through 16-4, one or more wide area networks (WAN), and oneor more local area networks (LAN). The passive wireless sensors 16-1through 16-4, when activated, sense one or more of a variety ofconditions. For example, one passive wireless sensor senses for thepresence, absence, and/or amount of moisture in a given location (e.g.,in a room, in a manufactured item or component thereof (e.g., avehicle), in a bed, in a diaper, etc.). As another example, a passivewireless sensor senses pressure on and/or in a particular item (e.g., ona seat, on a bed, in a tire, etc.).

As yet another example, a passive wireless sensor senses temperaturewithin a space and/or of an item (e.g., surface temperature of the item,in a confined space such as a room or a box, etc.). As a furtherexample, a passive wireless sensor senses humidity within a space (e.g.,a room, a closet, a box, a container, etc.). As a still further example,a passive wireless sensor senses the presence and/or percentages of agas within a space (e.g., carbon monoxide in a car, carbon monoxide in aroom, gas within a food container, etc.). As an even further example, apassive wireless sensor senses the presence and/or percentages of alight within a space. As yet a further example, a passive wirelesssensor senses the presence, percentages, and/or properties of one ormore liquids in a solution. In one more example, a passive wirelesssensor senses location proximity of one item to another and/or theproximity of the passive wireless sensor to an item (e.g., proximity toa metal object, etc.).

In general, the sensor computing devices 12 function to collect thesensed data from the passive wireless sensors and process the senseddata. For example, a passive wireless sensor generates a coded valuerepresentative of a sensed condition (e.g., amount of moisture). Asensor computing device 12 receives the coded value and processes it todetermine an accurate measure of the sensed condition (e.g., a valuecorresponding to the amount of moisture such as 0% saturated, 50%saturated, 100% saturated, etc.).

The user computing devices 14 communicate with one or more of the sensorcomputing devices 12 to gather the accurate measures of sensedconditions for further processing. For example, assume that the wirelesscommunication system is used by a manufacturing company that hasmultiple locations for assembly of its products. In particular, LAN 1 isat a first location where a first set of components of products areprocessed and the LAN 2 is at a second location where second componentsof the products and final assembly of the products occur. Further assumethat the corporate headquarters of the company is at a third location,where it communicates with the first and second locations via the WANand LANs.

In this example, the sensor computing device 12 coupled to LAN 1collects and processes data regarding the first set of components assensed by passive wireless sensors 16-1 and 16-2. The sensor computingdevice 12 is able to communicate this data to the user computing device14 coupled to the LAN 1 and/or to the computing device 14 at corporateheadquarters via the WAN. Similarly, the sensor computing device 12coupled to LAN 2 collects and processes data regarding the second set ofcomponents and final assembly as sensed by passive wireless sensors 16-3and 16-4. This sensor computing device 12 is able to communicate thisdata to the user computing device 14 coupled to the LAN 2 and/or to thecomputing device 14 at corporate headquarters via the WAN. In such asystem, real time monitor is available locally (e.g., via the LAN) andis further available non-locally (e.g., via the WAN). Note that any ofthe user computing devices 14 may receive data from the any of thesensor computing devices 12 via a combination of LANs and the WAN.

FIG. 2 is a schematic block diagram of an embodiment of a computingdevice 12 and/or 14 that includes a computing core 20, one or more inputdevices 48 (e.g., keypad, keyboard, touchscreen, voice to text, etc.),one or more audio output devices 50 (e.g., speaker(s), headphone jack,etc.), one or more visual output devices 46 (e.g., video graphicsdisplay, touchscreen, etc.), one or more universal serial bus (USB)devices, one or more networking devices (e.g., a wireless local areanetwork (WLAN) device 54, a wired LAN device 56, a wireless wide areanetwork (WWAN) device 58 (e.g., a cellular telephone transceiver, awireless data network transceiver, etc.), and/or a wired WAN device 60),one or more memory devices (e.g., a flash memory device 62, one or morehard drives 64, one or more solid state (SS) memory devices 66, and/orcloud memory 96), one or more peripheral devices, and/or a transceiver70.

The computing core 20 includes a video graphics processing unit 28, oneor more processing modules 22, a memory controller 24, main memory 26(e.g., RAM), one or more input/output (I/O) device interface module 36,an input/output (I/O) interface 32, an input/output (I/O) controller 30,a peripheral interface 34, one or more USB interface modules 38, one ormore network interface modules 40, one or more memory interface modules42, and/or one or more peripheral device interface modules 44. Each ofthe interface modules 36-44 includes a combination of hardware (e.g.,connectors, wiring, etc.) and operational instructions stored on memory(e.g., driver software) that is executed by the processing module 22and/or a processing circuit within the respective interface module. Eachof the interface modules couples to one or more components of thecomputing device 12-14. For example, one of the IO device interfacemodules 36 couples to an audio output device 50. As another example, oneof the memory interface modules 42 couples to flash memory 62 andanother one of the memory interface modules 42 couples to cloud memory68 (e.g., an on-line storage system and/or on-line backup system).

The transceiver 70 is coupled to the computing core 20 via a USBinterface module 38, a network interface module 40, a peripheral deviceinterface module 44, or a dedicated interface module (not shown).Regardless of how the transceiver 70 is coupled to the computing core,it functions to communicate with the passive wireless sensors.

FIG. 3 is a schematic block diagram of an example of a sensor computingdevice 12 communicating with a passive wireless sensor 16 (e.g., any oneof 16-1 through 16-4). The sensor computing device 12 is illustrated ina simplified manner; as such, it shown to include the transceiver 70, anantenna 96, the processing module 22, and the memory (e.g., one or more26 and 62-68). The passive wireless sensor 16 includes a radio frequency(RF) receiving circuit 75, one or more sensing elements 58, a processingmodule 84, and a memory 88. The RF receiving circuit 75 is operable toreceive a radio frequency (RF) signal 61 that has a carrier frequency ofa plurality of carrier frequencies 67. The RF receiving circuit includesa plurality of components and the impedance of those componentsestablish a resonant frequency of the RF receiving circuit.

In an example, the sensing element 58 of the passive wireless sensor 16senses an environmental condition 65 of an object. The environmentalcondition includes, but is not limited to, one or more of moisture,temperature, pressure, humidity, altitude, sonic wave (e.g., sound),human contact, surface conditions, tracking, location (e.g., proximity),etc. The object includes one or more of, but is not limited to, a box, apersonal item (e.g., clothes, diapers, etc.), a pet, an automobilecomponent, an article of manufacture, an item in transit, etc. Thesensing element 58 senses the environmental condition (e.g., moisture)and, as a result of the sensed condition, the sensing element 58 affectsan operational parameter (e.g., input impedance, quality factor,frequency, etc.) of the plurality of components of the RF receivingcircuit 75. As a specific example, the sensing element 58, as a resultof the sensed environmental condition 65, causes an impedance effect 63on the RF receiving circuit 75 that affects the resonant frequency ofthe RF receiving circuit 75.

The processing module 84 is operable to determine a first value for anadjustable element of a plurality of elements for a known environmentalcondition based on the resonant frequency of the RF receiving circuitand the carrier frequency of the RF signal. The plurality of elementsincludes the plurality of carrier frequencies 67 and the impedances ofthe plurality of components of the RF receiving circuit (e.g.,capacitor, antenna, and/or inductor of the RF receiving circuit). Inthis example, one of the components of the plurality of elements isadjustable and the other elements of the plurality of elements are fixedelements. To determine the first value, the processing module may, for arange of values for the adjustable element, determine power levels forthe received RF signal, and identify a value of the range of valuescorresponding to a peak power level of the power levels as the firstvalue.

The processing module 84 then determines a second value for theadjustable element for an unknown environmental condition based on theresonant frequency and the carrier frequency. To determine the secondvalue, the processing module determines, for a range of values for theadjustable element, power levels for the received RF signal, andidentifies a value of the range of values corresponding to a peak powerlevel of the power levels as the second value.

The processing module 84 is then determines a difference between thefirst and second values that corresponds to a change between the knownenvironmental condition and the unknown environmental condition. Theamount of the change is reflective of the level of the environmentalcondition (e.g., a little change corresponds to a little moisture; alarge change corresponds to a large amount of moisture). The processingmodule 84 generates a coded value to represent the amount of adjustmentand conveys the coded value to the sensor computing device 12.

FIG. 4 is a schematic block diagram of an embodiment of another exampleof the sensor computing device 12 communicating with the passivewireless sensor (e.g., any one of 16-1 through 16-4). The passivewireless sensor 16 includes a radio frequency (RF) receiving circuit 75,one or more sensing elements 58, a processing module 84, and a memory88. The RF receiving circuit includes a plurality of components whichmay include an antenna 80, a power harvesting circuit 82, a powerdetection circuit 86, a tuning circuit 90, a receiver section 92, and/ora transmitter section 94.

In an example, the sensing element 58 of the passive wireless sensor 16senses an environmental condition of an object. The environmentcondition includes, but is not limited to, one or more of moisture,temperature, pressure, humidity, altitude, sonic wave (e.g., sound),human contact, surface conditions, tracking, location, etc. The objectincludes one or more of, but is not limited to, a box, a personal item(e.g., clothes, diapers, etc.), a pet, an automobile component, anarticle of manufacture, an item in transit, etc. The sensing element 58senses the environmental condition (e.g., moisture) and, as a result ofthe sensed condition, the sensing element 58 affects an operationalparameter (e.g., input impedance, quality factor, frequency, etc.) of anRF front end of the passive wireless sensor. Note that the RF front endincludes one or more of the antenna 80, the tuning circuit 90, thetransmitter section 94, the receiver section 92.

As a specific example, the sensing element 58, as a result of the sensedenvironmental condition 65, causes an impedance effect on the RFreceiving circuit 75, an effect on the input impedance of the antennastructure 80 and/or of the tuning circuit 90 (e.g., a tank circuit thatincludes one or more capacitors and one or inductors having a resonantfrequency corresponding to the carrier frequency of the RF signal). Inresponse to the impedance change, the processing module 84 determines afirst value for an adjustable element of a plurality of elements for aknown environmental condition based on the resonant frequency of the RFreceiving circuit and the carrier frequency of the RF signal. Theprocessing module then determines a second value for the adjustableelement for an unknown environmental condition based on the resonantfrequency and the carrier frequency. The processing module 84 is thenable to determine a difference between the first and second values thatcorresponds to a change between the known environmental condition andthe unknown environmental condition. The amount of adjustment isreflective of the level of the environmental condition (e.g., a littlechange corresponds to a little moisture; a large change corresponds to alarge amount of moisture). The processing module 84 generates a codedvalue, the adjusted impedance, or other representation of the adjustedimpedance, to represent the amount of adjustment and conveys the codedvalue to the sensor computing device 12 via the transmitter section 94and the antenna 80 using back-scattering.

In addition to processing the sensed environmental condition, theprocessing module 84 processes a power level adjustment. For example,the power detection circuit 86 detects a power level of the received RFsignal. In one embodiment, the processing module interprets the powerlevel and communicates with the sensor computing device 12 to adjust thepower level of the RF signal transmitted by the computing device 12 to adesired level (e.g., optimal for accuracy in detecting the environmentalcondition). In another embodiment, the processing module 84 includes thereceived power level data with the environmental sensed data it sends tothe sensor computing device 12 so that the computing device can factorthe power level into the determination of the environmental condition.

FIG. 5 is a schematic block diagram of an example of a plurality ofcomponents of a radio frequency (RF) receiving circuit. The plurality ofcomponents of the RF receiving circuit includes an antenna operable toreceive an RF signal, and a tuning circuit. The inductance of antenna 80is coupled to a capacitor 93 (e.g., one or more of a varactor and aselectable capacitor bank) to form a tank circuit 97. The tuning circuit90 includes an adjusting circuit 91. When the antenna 80 corresponds tothe adjustable element, the adjusting circuit 91 adjusts thecharacteristics of the antenna to affect the resonant frequency. Whenthe capacitor 93 corresponds to the adjustable element, the adjustingcircuit 91 adjusts the capacitance of the capacitor 93 to affect theresonant frequency. Alternatively, a processing module of the sensorcomputing device is operable to adjust the characteristics of theantenna or the capacitance.

FIG. 6 is a schematic block diagram of another example of a plurality ofcomponents of a radio frequency (RF) receiving circuit. The plurality ofcomponents of the RF receiving circuit includes an antenna 90 operableto receive an RF signal, and a tuning circuit. The tuning circuit 90includes an adjusting circuit 91, a capacitor 93 (e.g., one or more of avaractor and a selectable capacitor bank), and an inductor 95. Thecapacitor 93 and the inductor 95 are coupled to form a tank circuit 97that is operably coupled to the antenna 80.

When the antenna corresponds to the adjustable element, the adjustingcircuit 91 adjusts the characteristics of the antenna 80 to affect theresonant frequency. When the capacitor 93 corresponds to the adjustableelement, the adjusting circuit 91 adjusts the capacitance of thecapacitor 93 to affect the resonant frequency. When the inductor 95corresponds to the adjustable element, the adjusting circuit 91 adjustsinductance of the inductor 95 to affect the resonant frequency.Alternatively, a processing module of the sensor computing device isoperable to adjust the characteristics of the antenna, the capacitance,or the inductor.

FIG. 7 is a logic diagram of an example of determining a change in anenvironmental condition. The method begins at step 98 where a wirelesssensor (e.g., the passive wireless sensor 16) receives a radio frequency(RF) signal having a carrier frequency of a plurality of carrierfrequencies. An RF receiving circuit of the wireless sensor includes aplurality of components, and the impedance of those components establisha resonant frequency of the RF receiving circuit. A sensing element ofthe wireless sensor is proximally positioned with respect to the RFreceiving circuit and to sense an environmental condition. When thesensing element is exposed to the environmental condition, the sensingelement affects the resonant frequency of the RF receiving circuit. Theenvironmental condition includes, but is not limited to, one or more ofmoisture, temperature, pressure, humidity, altitude, sonic wave (e.g.,sound), human contact, surface conditions, tracking, location,proximity, etc.

The method continues at step 100 where the wireless sensor determines afirst value for an adjustable element of a plurality of elements for aknown environmental condition based on the resonant frequency of the RFreceiving circuit and the carrier frequency of the RF signal. Theplurality of elements includes the plurality of carrier frequencies andthe impedances of the plurality of components of the RF receivingcircuit. One of the components of the plurality of elements isadjustable and the other elements of the plurality of elements are fixedelements. For example, the plurality of components of the RF receivingcircuit may include an antenna operable to receive an RF signal, acapacitor e.g., one or more of a varactor and a selectable capacitorbank), and/or an inductor. When the antenna corresponds to theadjustable element, the characteristics of the antenna are adjusted toaffect the resonant frequency. When the capacitor corresponds to theadjustable element, the capacitance is adjusted to affect the resonantfrequency. When the inductor corresponds to the adjustable element, theinductance is adjusted to affect the resonant frequency. Further, thewireless sensor may request a change in the carrier frequency of the RFsignal, when the carrier frequency corresponds to the adjustableelement.

To determine the first value, the processing module may, for a range ofvalues for the adjustable element, determine power levels for thereceived RF signal, and identify a value of the range of valuescorresponding to a peak power level of the power levels as the firstvalue.

The method continues at step 102 where the wireless sensor determines asecond value for the adjustable element for an unknown environmentalcondition based on the resonant frequency and the carrier frequency. Todetermine the second value, the processing module may, for a range ofvalues for the adjustable element, determine power levels for thereceived RF signal, and identify a value of the range of valuescorresponding to a peak power level of the power levels as the secondvalue.

The method continues at step 104 where the wireless sensor determines adifference between the first and second values that corresponds to achange between the known environmental condition and the unknownenvironmental condition. The amount of the change is reflective of thelevel of the environmental condition (e.g., a little change correspondsto a little moisture; a large change corresponds to a large amount ofmoisture).

It is noted that terminologies as may be used herein such as bit stream,stream, signal sequence, etc. (or their equivalents) have been usedinterchangeably to describe digital information whose contentcorresponds to any of a number of desired types (e.g., data, video,speech, audio, etc. any of which may generally be referred to as‘data’).

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “configured to”, “operably coupled to”, “coupled to”, and/or“coupling” includes direct coupling between items and/or indirectcoupling between items via an intervening item (e.g., an item includes,but is not limited to, a component, an element, a circuit, and/or amodule) where, for an example of indirect coupling, the intervening itemdoes not modify the information of a signal but may adjust its currentlevel, voltage level, and/or power level. As may further be used herein,inferred coupling (i.e., where one element is coupled to another elementby inference) includes direct and indirect coupling between two items inthe same manner as “coupled to”. As may even further be used herein, theterm “configured to”, “operable to”, “coupled to”, or “operably coupledto” indicates that an item includes one or more of power connections,input(s), output(s), etc., to perform, when activated, one or more itscorresponding functions and may further include inferred coupling to oneor more other items. As may still further be used herein, the term“associated with”, includes direct and/or indirect coupling of separateitems and/or one item being embedded within another item.

As may be used herein, the term “compares favorably”, indicates that acomparison between two or more items, signals, etc., provides a desiredrelationship. For example, when the desired relationship is that signal1 has a greater magnitude than signal 2, a favorable comparison may beachieved when the magnitude of signal 1 is greater than that of signal 2or when the magnitude of signal 2 is less than that of signal 1. As maybe used herein, the term “compares unfavorably”, indicates that acomparison between two or more items, signals, etc., fails to providethe desired relationship.

As may also be used herein, the terms “processing module”, “processingcircuit”, “processor”, and/or “processing unit” may be a singleprocessing device or a plurality of processing devices. Such aprocessing device may be a microprocessor, micro-controller, digitalsignal processor, microcomputer, central processing unit, fieldprogrammable gate array, programmable logic device, state machine, logiccircuitry, analog circuitry, digital circuitry, and/or any device thatmanipulates signals (analog and/or digital) based on hard coding of thecircuitry and/or operational instructions. The processing module,module, processing circuit, and/or processing unit may be, or furtherinclude, memory and/or an integrated memory element, which may be asingle memory device, a plurality of memory devices, and/or embeddedcircuitry of another processing module, module, processing circuit,and/or processing unit. Such a memory device may be a read-only memory,random access memory, volatile memory, non-volatile memory, staticmemory, dynamic memory, flash memory, cache memory, and/or any devicethat stores digital information. Note that if the processing module,module, processing circuit, and/or processing unit includes more thanone processing device, the processing devices may be centrally located(e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that if the processing module, module, processing circuit,and/or processing unit implements one or more of its functions via astate machine, analog circuitry, digital circuitry, and/or logiccircuitry, the memory and/or memory element storing the correspondingoperational instructions may be embedded within, or external to, thecircuitry comprising the state machine, analog circuitry, digitalcircuitry, and/or logic circuitry. Still further note that, the memoryelement may store, and the processing module, module, processingcircuit, and/or processing unit executes, hard coded and/or operationalinstructions corresponding to at least some of the steps and/orfunctions illustrated in one or more of the Figures. Such a memorydevice or memory element can be included in an article of manufacture.

One or more embodiments have been described above with the aid of methodsteps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claims. Further, the boundariesof these functional building blocks have been arbitrarily defined forconvenience of description. Alternate boundaries could be defined aslong as the certain significant functions are appropriately performed.Similarly, flow diagram blocks may also have been arbitrarily definedherein to illustrate certain significant functionality.

To the extent used, the flow diagram block boundaries and sequence couldhave been defined otherwise and still perform the certain significantfunctionality. Such alternate definitions of both functional buildingblocks and flow diagram blocks and sequences are thus within the scopeand spirit of the claims. One of average skill in the art will alsorecognize that the functional building blocks, and other illustrativeblocks, modules and components herein, can be implemented as illustratedor by discrete components, application specific integrated circuits,processors executing appropriate software and the like or anycombination thereof.

In addition, a flow diagram may include a “start” and/or “continue”indication. The “start” and “continue” indications reflect that thesteps presented can optionally be incorporated in or otherwise used inconjunction with other routines. In this context, “start” indicates thebeginning of the first step presented and may be preceded by otheractivities not specifically shown. Further, the “continue” indicationreflects that the steps presented may be performed multiple times and/ormay be succeeded by other activities not specifically shown. Further,while a flow diagram indicates a particular ordering of steps, otherorderings are likewise possible provided that the principles ofcausality are maintained.

The one or more embodiments are used herein to illustrate one or moreaspects, one or more features, one or more concepts, and/or one or moreexamples. A physical embodiment of an apparatus, an article ofmanufacture, a machine, and/or of a process may include one or more ofthe aspects, features, concepts, examples, etc. described with referenceto one or more of the embodiments discussed herein. Further, from figureto figure, the embodiments may incorporate the same or similarly namedfunctions, steps, modules, etc. that may use the same or differentreference numbers and, as such, the functions, steps, modules, etc. maybe the same or similar functions, steps, modules, etc. or differentones.

While the transistors in the above described figure(s) is/are shown asfield effect transistors (FETs), as one of ordinary skill in the artwill appreciate, the transistors may be implemented using any type oftransistor structure including, but not limited to, bipolar, metal oxidesemiconductor field effect transistors (MOSFET), N-well transistors,P-well transistors, enhancement mode, depletion mode, and zero voltagethreshold (VT) transistors.

Unless specifically stated to the contra, signals to, from, and/orbetween elements in a figure of any of the figures presented herein maybe analog or digital, continuous time or discrete time, and single-endedor differential. For instance, if a signal path is shown as asingle-ended path, it also represents a differential signal path.Similarly, if a signal path is shown as a differential path, it alsorepresents a single-ended signal path. While one or more particulararchitectures are described herein, other architectures can likewise beimplemented that use one or more data buses not expressly shown, directconnectivity between elements, and/or indirect coupling between otherelements as recognized by one of average skill in the art.

The term “module” is used in the description of one or more of theembodiments. A module implements one or more functions via a device suchas a processor or other processing device or other hardware that mayinclude or operate in association with a memory that stores operationalinstructions. A module may operate independently and/or in conjunctionwith software and/or firmware. As also used herein, a module may containone or more sub-modules, each of which may be one or more modules.

While particular combinations of various functions and features of theone or more embodiments have been expressly described herein, othercombinations of these features and functions are likewise possible. Thepresent disclosure is not limited by the particular examples disclosedherein and expressly incorporates these other combinations.

What is claimed is:
 1. A wireless sensor comprises: a radio frequency(RF) receiving circuit operable to receive an RF signal having a carrierfrequency, the RF receiving circuit includes a variable impedance,wherein impedance of the variable impedance is a factor in establishinga resonant frequency of the RF receiving circuit; and a processingmodule operably coupled to the RF receiving circuit, wherein theprocessing module is operable to: determine a first value for a firstimpedance of the variable impedance for a known temperature based on theresonant frequency and the carrier frequency; determine a second valuefor a second impedance of the variable impedance for an unknowntemperature based on the resonant frequency and the carrier frequency;and determine a difference between the first and second values thatcorresponds to a change between the known temperature and the unknowntemperature.
 2. The wireless sensor of claim 1, wherein the variableimpedance comprises: an antenna operable to receive the RF signal; and avariable capacitor coupled to the antenna to form a tank circuit.
 3. Thewireless sensor of claim 2, wherein the first impedance is establishedby characteristics of the variable impedance.
 4. The wireless sensor ofclaim 2, wherein the second impedance is established by adjustingcharacteristics of the variable impedance.
 5. The wireless sensor ofclaim 1, wherein the variable impedance comprises: an antenna operableto receive the RF signal; a variable capacitor; and an inductor, whereinthe variable capacitor and at least one of the antenna and the inductorare coupled to form a tank circuit.
 6. The wireless sensor of claim 5,wherein the first impedance is established by characteristics of thevariable impedance.
 7. The wireless sensor of claim 5, wherein thesecond impedance is established by adjusting characteristics of thevariable impedance.
 8. The wireless sensor of claim 1, wherein theprocessing module is further operable to determine the first value by:for a range of values for the first impedance, determining power levelsfor the received RF signal; and identifying a value of the range ofvalues corresponding to a peak power level of the power levels as thefirst value.
 9. The wireless sensor of claim 1, wherein the processingmodule is further operable to determine the second value by: for a rangeof values for the second impedance, determining power levels for thereceived RF signal; and identifying a value of the range of valuescorresponding to a peak power level of the power levels as the secondvalue.
 10. A method for execution by a wireless sensor, the methodcomprises: receiving a radio frequency (RF) signal having a carrierfrequency, wherein an RF receiving circuit of the wireless sensorincludes a variable impedance, wherein impedance of the variableimpedance is a factor in establishing a resonant frequency of the RFreceiving circuit; determining a first value for a first impedance ofthe variable impedance for a known temperature based on the resonantfrequency and the carrier frequency; determining a second value for asecond impedance of the variable impedance for an unknown temperaturebased on the resonant frequency and the carrier frequency; anddetermining a difference between the first and second values thatcorresponds to a change between the known temperature and the unknowntemperature.
 11. The method of claim 10, wherein the variable impedancecomprises: an antenna operable to receive the RF signal; and a variablecapacitor coupled to the antenna to form a tank circuit.
 12. The methodof claim 11, wherein the first impedance is established bycharacteristics of the variable impedance.
 13. The method of claim 11,wherein the second impedance is established by adjusting characteristicsof the variable impedance.
 14. The method of claim 10, wherein thevariable impedance comprises: an antenna operable to receive the RFsignal; a variable capacitor; and an inductor, wherein the variablecapacitor and at least one of the antenna and the inductor are coupledto form a tank circuit.
 15. The method of claim 14, wherein the firstimpedance is established by characteristics of the variable impedance.16. The method of claim 14, wherein the second impedance is establishedby adjusting characteristics of the variable impedance.
 17. The methodof claim 10, wherein the determining the first value further comprises:for a range of values for the first impedance, determining power levelsfor the received RF signal; and identifying a value of the range ofvalues corresponding to a peak power level of the power levels as thefirst value.
 18. The method of claim 10, wherein the determining thesecond value further comprises: for a range of values for the secondimpedance, determining power levels for the received RF signal; andidentifying a value of the range of values corresponding to a peak powerlevel of the power levels as the second value.